PleiAlps - Deriving 3D forest parameters from Pléiades imagery

Mountain forests provide a wide range of ecosystem services in terms of protective, productive, social and economic functions. Additionally, they are a major factor in the CO2 balance and their change needs to be considered in international reporting. Therefore, a comprehensive knowledge of forest dynamics is required to monitor and better understand interactions between forests, human activities, and the atmosphere.

Monitoring of forests is therefore of very high importance. To quantify the services provided, detailed knowledge of e.g. forest gaps, tree height, and crown coverage are required with high spatial and temporal resolution. Current monitoring approaches are commonly based on statistical analyses of National Forest Inventory (NFI) data, which are based on high precision field measurements for sample plots and are therefore not able to provide the required spatial resolution. While airborne laser scanning (ALS) and digital imaging can provide the necessary geometric resolution, they cannot provide an Alpine coverage within a vegetation period. National update cycles of aerial imagery are in the order of 3 years and more. Above that, no homogeneous 3D datasets exist yet for the entire Alpine region, and thus also no homogeneous forest 3D parameters.

The lack of detailed, cross-border, up-to-date forest parameters for assessing their services builds the motivation for the exploratory project PleiAlps. Pléiades satellite stereo images show a great potential for meeting those demands, because of the agility of the sensor, its high sub-meter resolution, and the large area coverage in one swath. The guiding idea of this exploratory project  is to establish Alpine forest maps showing at high resolution 3D parameters derived from satellite stereo-imaging technology.

PleiAlps will lead to a deeper understanding of the requirements for generating an Alpine-wide, high-detail forest map and its quality. In the long run, this shall be embedded in change detection and the realization of forest information on ecosystem services overarching the entire Alps.